The present invention pertains to the preparation of glycidyl derivatives of aromatic compounds containing an active hydrogen atom reactive with an epihalohydrin.
The preparation of glycidyl ethers by the reaction of an aromatic hydroxyl-containing compound with epihalohydrin in the presence of a base is well known as disclosed by Lee and Neville in HANDBOOK OF EPOXY RESINS, McGraw-Hill, 1967.
Improvements in the process for the preparation of epoxy resins have been made by Vargiu et al. in U.S. Pat. No. 4,017,523 who prepared epoxy resins having low hydrolyzable chloride by removing the excess epihalohydrin from the preparation of the halohydrin intermediate product and dissolving it in a solvent prior to dehydrohalogenation. Caskey et al. in U.S. Pat. No. 4,447,598 prepared epoxy resins low in hydrolyzable chloride contents by employing a second dehydrohalogenation step. Wang et al. prepared epoxy resins by reacting the phenolic hydroxyl-containing compound with an epihalohydrin in the presence of an alkali metal hydroxide and a solvent which codistills with water and epihalohydrin.
The preparation of an epoxy resin by these methods generates large quantities of alkali metal halide salts which must be removed from the resin or vice versa. The solid salt formed during the reaction is usually removed by mechanical means such as filtration or centrifugation. This is relatively expensive equipment to purchase in order to manufacture these epoxy resins on a commercial scale. It would therefore be desirable to have a method for the preparation of these epoxy resins which did not require the use of the mechanical equipment for removing the salt from the epoxy resin or for removing the epoxy resin from the salt.